Aldon Smith said his first sack in Sunday's 27-13 win over Miami had two elements: speed and power.

It was actually pretty heavy on power.

On the first play of the second quarter, the 49ers' 258-pound outside linebacker bull-rushed 312-pound rookie left tackle Jonathan Martin into the backfield and dropped quarterback Ryan Tannehill to take sole possession of the franchise record with 18 1/2 sacks.

"He got me on that one bull rush pretty good," Martin said. "There is a reason why he is one of the best pass rushers in the league."

Smith added another sack in the fourth quarter to bring his season total to 19 1/2, tied for ninth most in NFL history. With three regular-season games left, Smith needs 3 1/2 sacks to break the league record set by Giants defensive end Michael Strahan in 2001.

Smith acknowledged the record is on his radar.

"I'm human," he said, "so it's going to cross my mind."

Dobbs injured: Reserve defensive tackle Demarcus Dobbs was carted to the locker room after he sustained a right-knee injury in the third quarter. Dobbs, who was on crutches after the game, said he'd have an MRI exam Monday, but head coach Jim Harbaugh was optimistic his injury wouldn't end his season.

"We might have dodged a bullet," he said.

Gore's fashion statement: After the game, running back Frank Gore - a Miami resident - was wearing an interesting sweatshirt. It sported a cartoon of an upside-down dolphin with X'd out eyes (the universal cartoon symbol for death).

"I had this before the season," Gore said. "I knew we had the Dolphins on the schedule. I said, 'We've got to flip them upside down when we play them.' "

Gore, who had 85 total yards, did his part. In the third quarter, he had a 1-yard scoring run and tied Roger Craig and Joe Perry for the most rushing touchdowns in franchise history (50).

Romo pays visit: The 49ers had a special guest in their locker room after the game. Sergio Romo, the Giants' reliever, paid a visit and looked like a true fan. He was wearing an Aldon Smith jersey and carried a football for collecting signatures.

The 49ers were excited to see him, posing for photos and happily signing the football.

"Best beard in the business," left tackle Joe Staley said. "It's fun when we win, we have a few celebrities coming in here. We had (actors) Vince Vaughn and Owen Wilson. Now we've got Sergio Romo."

Briefly: Quarterback Alex Smith and Miami running back Reggie Bush had a long postgame conversation at midfield. Bush and Smith were teammates at Helix High in San Diego. ... As expected, wide receiver Mario Manningham (shoulder) was inactive after he failed to practice during the week. ... Wide receiver A.J. Jenkins played his first NFL snaps, but did not record his first career reception. The first-round pick had been active for two previous games, but didn't play.